Key points for wall thickness design and mold shrinkage of T-shaped groove lined cast iron platform

The main reason for the deformation of the T-shaped groove marking cast iron platform is the uneven wall thickness or poor stiffness of the casting. So when designing such cast iron platform castings, designing the cross-section in a symmetrical shape or adding auxiliary plates to improve the stiffness structure can prevent deformation. Is the connection design of the T-shaped groove marking cast iron platform wall correct to prevent defects such as shrinkage, porosity, deformation, cracks, and sand sticking on the T-shaped groove marking cast iron platform, and to improve the quality of the cast iron flat plate; The quality of castings has a significant impact. Special attention should be paid to the following aspects in the design of cast iron platforms:

In addition, gray iron metal is prone to producing columnar crystals, with crystals intersecting at right angles, weak bonding between crystals, decreased mechanical properties at platform corners, and the formation of cracks. Rounded corners are also conducive to modeling, avoiding sand holes caused by damage to the sharp corners of the mold, affecting the welding plate  beautiful.

In order to reduce heat savings and avoid defects such as shrinkage and looseness in castings, the connection of rib plates on the platform should avoid crossing as much as possible. The connection of the reinforcing plate should use circular joints.

The inter wall connections of the T-shaped groove marking cast iron platform should have casting rounded corners. The T-shaped groove platform with no rounded corner structure accumulates cast iron at the right angle, and the hot spot circle is larger than elsewhere, which is prone to shrinkage and porosity. In addition, stress concentration is severe at the inner corner, which is prone to cracking.

3. The connection between thick and thin walls should gradually transition. When designing cast iron platform castings, if the wall thickness cannot be uniformly distributed, the connection between thick and thin walls should adopt a gradual transition method to avoid stress concentration and cracks. The surface quenching of gray cast iron marking platform can improve its hardness, and the quenching hardness of gray iron 250 material can reach HB210 or above In order to improve the surface hardness, properties, and fatigue strength of certain castings, surface quenching can be used. Both gray cast iron plates and ductile iron plates can undergo surface quenching.

The T-shaped groove marking cast iron platform casting should be normalized (pre heat treated) before surface quenching, so that the amount of pearlite in the BAOZHENG matrix structure can reach more than 75%, which can achieve good surface quenching effect. When quenching and cooling, the heating layer on the surface of BAOZHENG should be able to fully complete the martensitic transformation without causing quenching cracks, so it should generally not be cooled through. When using water spray cooling, stop spraying water at 250 ℃ and use quenching waste heat for self tempering. It can also be sent to the tempering furnace for tempering in a timely manner after quenching.

When the T-shaped groove marking cast iron platform casting is hindered from shrinkage, it is not only affected by chemical composition, temperature, and phase transformation, but also by some external resistance. The shrinkage of T-shaped groove lined cast iron platform in the mold is only hindered by friction between the metal surface and the mold surface, which is called free shrinkage; If the shrinkage of the T-shaped groove lined cast iron platform in the mold is also hindered by other factors, it is called obstructed shrinkage. It is evident that for the same alloy, the hindered shrinkage rate is lower than the free shrinkage rate.

The resistance experienced by the T-shaped groove marking cast iron platform during shrinkage in the mold is as follows.

(1) Friction force on the surface of the mold. When the T-shaped groove marking cast iron platform shrinks, the frictional force between its surface and the mold surface is related to factors such as the weight of the welded plate, the smoothness of the mold surface, and the coating on the mold surface.

(2) Mechanical resistance. When the T-shaped groove marking cast iron platform shrinks, it is subject to the resistance of the mold and core, and cannot shrink freely. This resistance is called mechanical resistance. The magnitude of this resistance is determined by the strength and yielding of the mold and core, the position of the box stopper or core bone, and the thickness and length of the welded plate itself. Mechanical resistance reduces the shrinkage of the T-shaped groove marking cast iron platform.

(3) Thermal resistance. When the contraction time and speed of each part of the T-shaped groove platform are inconsistent, and they constrain each other to produce resistance and cannot contract freely, it is called thermal resistance. So the generation of thermal resistance is related to the welding of flat plate structures.

When designing the T-shaped groove marking flat plate process, the size of the pattern cannot be considered based on the free shrinkage rate. The casting shrinkage rate used in production is the actual shrinkage rate after considering various resistance effects.

To prevent deformation of YOUHAI, the working surface of the T-shaped groove marking cast iron platform should be adjusted to a horizontal plane as much as possible during support. After the inspection or marking is completed, the workpiece should be lifted down and not placed on the flat plate for a long time. After use, the working surface of the flat plate should be wiped clean in a timely manner, and then a layer of rust proof oil should be applied. If not used for a long time, apply a layer of butter and then spread a layer of white paper. A ZHUANYONG cover made of good wooden boards. When not in use, cover the flat plate with a cover and strictly prohibit water droplets from falling on the T-shaped groove marked cast iron platform